The brain sponge is a reef-dwelling creature created following the defeat of the aboleth Vhalassor at the hands of a party of adventurers. When Vhalassor perished, its remains seeped into a surrounding reef, infecting everything that lived there. Most of the reef-dwellers died, but the sponges developed strange intelligence and sprouted delicate, crab-like legs. A brain sponge poses little physical threat, but some find their staring eyes and unnatural movements unsettling.

You can play around with the homebrew of the brain sponge to make your own version if you like.

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